1. Field of the Invention
This invention relates to a zoom lens suitable for use with a digital still camera, a video camera, a monitoring camera or the like apparatus and an image pickup which includes a zoom lens.
2. Description of the Related Art
In recent years, the market of digital cameras has expanded greatly, and also demands of users for digital cameras are complicated. Demands not only for high picture quality, miniaturization and reduction in thickness but also for increase of the magnification and the image pickup angle of an image pickup lens have increased in recent years.
As one of zoom lenses, a zoom lens of the positive lead type wherein the lens group positioned nearest to the object side has a positive refracting power has an advantage that the zoom rate can be set to a high value. Therefore, the positive lead type zoom lens is used frequently as a zoom lens of the type suitable for such a high zoom rate as is higher than, for example, four times.
Particularly, a four-group zoom lens which includes four lens groups having positive, negative, positive and positive refracting powers in order from the object side is well known as a compact zoom lens of the positive lead type. Such four-group lenses are disclosed, for example, in Japanese Patent Laid-Open No. 2006-23529 (hereinafter referred to as Patent Document 1), Japanese Patent Laid-Open No. 2005-338740 (hereinafter referred to as Patent Document 2), Japanese Patent No. 3,977,150 (hereinafter referred to as Patent Document 3) and Japanese Patent Laid-Open No. 2006-308957 (hereinafter referred to as Patent Document 4).